1. Field of the Invention
The present invention relates to a multi-stage reciprocating vacuum pump including a housing, at least one first pump chamber and at least one second pump chamber provided in the housing and each having a suction side and an outlet side, a piston reciprocating in each of the at least one first pump chamber and the at least one second pump chamber, a valve provided at the outlet side of each of the at least one first pump chamber and at least one second pump chamber, and a conduit for communicating the outlet side of the at least one first pump chamber with the suction side of the at least one second pump chamber, and to a method of operating the pump.
2. Description of the Prior Art
As a rule, reciprocating vacuum pumps for pumping out a recipient between the atmospheric pressure and a desired end vacuum of, e.g., 10−2 mbar are formed with several stages. One of such pumps is disclosed, e.g., in U.S. Pat. No. 5,921,755. In such a pump, separate stages are arranged in a row in order to be able to provide for the necessary pressure difference. The suction capacity is determined by a pump stage adjacent to the recipient. The following, normally with a reduced suction capacity, pump stages provide for further compression of the delivered gases up to the atmospheric pressure. By a proper gradation, the power consumption of a pump can be reduced.
In order to start the pumping-out process when the pressure in the recipient is still close to 1000 mbar, it is not necessary to further compress the gas which is aspirated with the first piston. The following pump stages are bypassed by using a pressure controlled by-pass valve, and these pump stages need not to perform any compression. However, at this initial stage, a higher suction capacity would be advantageous for accelerating the pumping process.
Accordingly, an object of the present invention is to provide a multi-stage reciprocating vacuum pump in which all stages in each phase of the pumping process can be used in such a way that the pump characteristics are improved and an effective pumping takes place.
Another object of the invention is the provide a compact and space-saving construction of a reciprocating vacuum pump, with the connecting conduits having minimum lengths and a reduced flow resistance.
A further object of the present invention is to provide a reciprocating vacuum pump in which the condensation of liquid and the amount of solids in the connecting conduits are eliminated or at least are reduced to a minimum.